a) Field of the Invention
The present invention relates to an actuator or operating member for electronic musical instruments.
b) Description of the Related Art
Strings of a natural musical instrument, piano, are struck by hammers operated from a keyboard. The keyboard of an electronic musical instrument has a number of keys for playing the instrument. Musical tones to be produced by the instrument are controlled, for example, by detecting an initial touch of depressing a key (hereinafter called an operating member) and arm after-touch of strongly or deeply pushing the operating member while depressing it.
The initial touch of each operating member is detected as the depression velocity of the member by a two-make switch mounted under the member. The after-touch is detected by a pressure sensor mounted on a stopper which prevents each operating member from being depressed lower than predetermined position.
Examples of a conventional operating device for an electronic musical instrument are shown in FIGS. 5A and 5B.
An operating device shown in FIG. 5A has an operating member 6 which is rotatable about a fulcrum K formed on a support frame 2.
The operating member 6 is always forced to rotate in the counter clockwise direction as viewed in FIG. 5A by a spring 7. The upward and downward rotations of the operating member 6 are restricted by upper and lower stoppers 9A and 9B. Under the operating member 6, two switches 11A and 11B are mounted having different on-strokes.
An operating device shown in FIG. 5B has an operating member 6 with a thin neck portion K via which the member 6 is mounted on a support frame 2. When a force is applied to the operating member 6, it rotates in the clockwise direction about the neck portion K. Similar to the device shown in FIG. 5A, the upward and downward rotations of the operating member 6 are restricted by upper and tower stoppers 9A and 9B.
The initial touch of the operating member 6 shown in FIG. 5B is detected as the depression velocity by a two-make switch 11. The after-touch is detected by a pressure sensor mounted on the stopper 9B.
The performance of a player, expressed for example by a force applied to the operating member shown in FIG. 5A or 5B during the period from the detection of the initial touch to the detection of the after-touch, generates musical tones.
An electronic musical instrument can generate various kinds of musical tones. It is desirable that the operating member of the instrument can generate parameters suitable for controlling such various kinds of musical tones.
It is desirable, particularly for a continuous tone to be produced by a bow of a stringed instrument, to detect the details of a whole stroke of each operating member in order to reproduce the fidelity of the performance of a player, for example, by using the method of detecting a large amount of data during a whole stroke of each member.
FIG. 5C shows the relationship between the displacement amount of the operating member 6 shown in FIG. 5A or 5B and the depression force of a player. At the initial stage, for example, up to the displacement of 0.5 mm, the displacement of the operating member 6 is proportional to the depression force applied to it.
During the main depression stroke, after the initial stage up to the displacement of 10 mm, the depression force changes little.
After the displacement of 10 mm, the force increases greatly with a small displacement because of the abutment of the operating member with the stopper.
In the experiment result shown in FIG. 5C, the force applied to the operating member 6 was about 50 gram-weight at the displacement of 0.5 mm, and was about 70 gram-weight at the displacement of 10 mm.
FIG. 5D shows the relationship between the force and displacement of the operating member 6 during one stroke. In FIG. 5D, the solid line indicates the force applied by a player, and the one-dot-chain line indicates the detected displacement. The abscissa represents time, and the ordinate represents the displacement and force.
As shown in FIG. 5D, the displacement is proportional to the force applied by the player during the initial and final stages (up to 50 gram-weight).
However, during the range from 50 gram-weight to 70 gram weight, the displacement changes greatly, and thereafter during the range over 70 gram-weight, it changes little, although the force actually applied by the player changes as shown in FIG. 5D.
Therefore, if the musical tone is controlled in accordance with an output from a sensor, a change of the force applied to the operating member by a player is exaggerated during one range, and is almost neglected during the other range. Therefore, the intention of a player giving a performance including a continuous tone cannot be fully reflected upon the output of a sensor.
During the range from 0.5 mm to 10 mm, the displacement changes greatly with a change in the force applied to the operating member. Therefore, it is difficult to finely control the performance by changing the force.
In the above description, the depression force is applied to the same position of the operating member during one stroke. If the force applying position is changed during one stroke, a detected force changes even if the same force is applied. Namely, as the operating member is depressed at the position more remote from the fulcrum, the force applied to a sensor becomes large. However, there is a performance style which requires to control musical tones only by the depression force independent from the force applying position.
As described above, conventional operating members for an electronic musical instrument have often many restrictions of the performance which uses various kinds of musical tones.